How to check if a array key exists?

Question

How do I check if a key doesn't exist in javascript?

I have the below and I want to check if docs[3].created exists and has a value and if it does then add it to the thevalue variable.

With this, since docs[3].created doesn´t exits I get "Cannot read property 'created' of undefined" error.

var docs=[{ created: 2016-01-10, name: "Claes"},{ created: 2016-01-11, name: "Lisa"}];

var thevalue = docs[3].created;

I really need some help with this, thanks a lot!

You should update your question and tags to include which language you are asking about! — Govind Parmar, Jan 15 '17 at 19:03
Possible duplicate of [Checking if a key exists in a JavaScript object?](http://stackoverflow.com/questions/1098040/checking-if-a-key-exists-in-a-javascript-object) — rokas, Jan 15 '17 at 19:03
rokas. I might be but I don´t understand that, so thats why the question. — Claes Gustavsson, Jan 15 '17 at 19:10

score 0 · Accepted Answer · answered Jan 15 '17 at 19:19

docs is an array of objects. Each object has a created element. However, you try to get the created of the third item, while you only have two items, so possible valid indexes are 0 and 1. You could do something like this:

var docs=[{ created: 2016-01-10, name: "Claes"},{ created: 2016-01-11, name: "Lisa"}];

var thevalue = (docs.length > 3) ? docs[3].created : undefined;

This will result in undefined under the current settings and will get rid of the error. If your array had a third element, then this would store it into the variable.

How to check if a array key exists?

1 Answers1